When we arrived to assist a client with cleaning a grain silo – we were excited. The staff would be getting some Rope Access hours and no one had entered these silos in close to 8 years. The silo we were to enter had product stuck inside – about 20’ deep. The product had been stuck for close to 4 months.
In February 2015, WorkSafe BC added a new regulation to the OHS Regulations – Part 34, Rope Access. While it is defined in the regulations, generally working on rope in BC now falls under three categories; Bosun (Boatswain) Chair, Rope Access or Rescue. Ronin, due to our confined space and rescue backgrounds, regularly obtains rope access work in confined spaces.
When we opened this silo all of our training (except rescue – thankfully) would come into play. We opened the bottom hatch and broke through the four odd feet of product lining the walls of the silo. Once we broke through we inserted our monitor to take a reading (all work was outside of the silo at this time). We obtained readings of O2 – 1.7%, CO – 6ppm, LEL – +OL (over limit), H2S – 0. We immediately backed away from the space! As we were leaving our other monitor outside on the deck was getting O2 readings into the 20% range – outside of the space, 5’ away!
Under the direction of our CRSP and using IS fans we vented the space for 1.5 hours. During this time our CRSP, Level 3 rope access technician and lead rescue technician updated all documents. Hazard assessment, entry procedures, rope access plan, permits, gas monitor logs, rescue plan, etc – yes a small tree was sacrificed for safety of the crew. The crew also rigged the rope lines we would be using to enter and stay above the product in the silo.
After an hour and a half the space was reading CO up to 2ppm and O2 down to 20.3%. The concern we still had however was once we started moving product, would we see a return of the harmful atmosphere? I drew the short straw (who am I kidding, I pulled rank, who would not want to be the first to enter a potentially hazardous atmosphere for the first time ) and put on a supplied air respirator. I clipped into the ropes and ascended through the side opening into the silo. We were both monitoring from the outside as mentioned and I had a monitor on me also. I obtained the same readings as outside so started to work (still on air). As I started digging up the clumped product we did see blips of up to 6ppm of H2S and drops of O2 to the low 20%’s in the space.
We rotated in the space every hour to reduce fatigue from hanging on a rope, on air while digging grain that had been stuck together for 4 months. All in all a unique and entertaining job.